You may have already read about Mirrus‘ digital mirror installation at O’Hare Airport. A digital display shows a full screen advertisement, but when a person approaches the display, the ad shrinks to one corner and the display becomes a mirror. I like the fact it responds to people approaching it. Thankfully, there is no mention of touch interaction there — this is probably one type of installation where touch is definitely not appropriate! There are a number of videos on the web about the O’Hare installation including the one below:

The Mirrus website also shows something called CoolerVision which displays content on glass freezer doors in grocery stores. I think the addition of gesture response would be very effective in installations like this one.